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Isobaric Vapor–Liquid Equilibrium for Acetone + Methanol + Phosphate Ionic Liquids
Isobaric
vapor–liquid equilibrium (VLE) at atmospheric pressure
(101.3 kPa) for the binary systems of acetone + methanol, acetone
+ phosphate ionic liquids (ILs), and methanol + phosphate ILs, and
for the ternary system of acetone + methanol + phosphate ILs are measured
using a circulation VLE still. The phosphate ILs include 1,3-dimethylimidazolium
1,3-dimethylimidazolium dimethylphosphate ([MMIM]Â[DMP]), 1-ethyl-3-methylimidazolium
diethylphosphate ([EMIM]Â[DEP]), and 1-butyl-3-methylimidazolium dibutylphosphate
([BMIM]Â[DBP]). The addition of these phosphate ILs to the azeotropic
acetone + methanol system results in a salting-out effect on acetone
and makes the azeotropic point disappear. The relative volatility
α<sub>12</sub> of acetone over methanol increases with increasing
molar fraction of ILs. The equilibrium data were well fitted by the
electrolyte nonrandom two-liquid model (e-NRTL). Compared with some
reported ILs previously such as pyridinium hexafluorophosphate, imidazolium
trifluoromethane sulfonate and imidazolium dicyanamide, such imidazolium
phosphate ILs are fluorine-free, are prepared more simply with lower
cost, and make the azeotropic point disappear at less added amount
of ILs. This work shows that such phosphate ILs are a class of potential
solvents to separate azeotropic acetone + methanol system